This invention relates to a method and apparatus for providing reliable authentication of a document, and for verifying the authenticity of a document, by using a unique encrypted code which is created and affixed to the document.
It is well known that corporate documents, particularly negotiable instruments such as checks and stock certificates, are susceptible to counterfeiting. With the advent of high-quality, low-cost color computer printers, this problem has become even more acute. Printers of negotiable instruments (including commercial check printers and the U.S. Bureau of Printing and Engraving) have introduced a variety of anti-counterfeiting devices into their paper and/or printed designs. Examples of such devices include color-shifting ink, holographic strips, watermarking, and microprinting. These measures naturally add to the complexity and production cost of the documents, while at the same time the security they provide is constantly being eroded by more sophisticated counterfeiting techniques. Accordingly, there is a need for a reliable, efficient, and cost-effective solution to the problem of counterfeit negotiable instruments.
In addition, in the case of a check, for example, even if the blank check is genuine, the recipient still has a need to determine whether items such as the date, the amount, and the name of the payee, are as written by the issuer or have been subsequently altered.
A number of methods and devices for authenticating documents (including negotiable instruments such as checks) have recently been proposed. Examples of devices which cryptographically certify the authenticity and integrity of electronic documents may be found in U.S. Pat. Nos. 5,189,700; 5,157,726; 5,136,643; 5,136,647; 5,136,646; 5,022,080; 5,001,752; and 4,786,940. These patents disclose devices that input image data in digital form, cryptographically certify the digital data (for example, by adding and hashing additional data representing a certificate with a representation of a document), and output a digital message. Use of these devices generally requires that the document image be input to the device in digital form. Accordingly, the use of such data certification devices with paper documents would require the addition of a document scanner to generate a representation of the document in digital form, leading to increased device cost and complexity.
Furthermore, because image data representing the document would be included in the cryptographic message, one wishing to verify the document data would also have to create a digital representation of the message--a costly and possibly impractical operation for those with limited capabilities. The complex problem of ensuring that the digitization of the document at the time of certification is the same digitization at the time of verification has not been reliably solved.
U.S. Pat. No. 5,388,158 discloses an apparatus that affixes to a document a label created by scanning the document and producing a digital signal; the digital signal is compressed, encrypted, and coded as a two-dimensional bar code. This apparatus, like those discussed just above, creates a digital representation of an image of the document, as opposed to using specific data from the document.
U.S. Pat. No. 5,341,428 discloses a document verification system in which information specific to a document is encrypted and printed on the document, and the recipient of the document is issued a "smart card" containing the encryption algorithm. A third party can then verify that the holder of the card is the legitimate holder of the document by inserting the card into a device which identifies the cardholder with the card and decrypts the message on the document. This system thus requires both a smart card and a terminal, and furthermore requires that the recipient of the document identify himself to a third party in order to obtain verification of the document. Such a system may be needlessly complex in many instances, and limits the number of persons who can verify the document to those holding smart cards with the appropriate algorithm.
A system for on-site printing of checks has recently been reported in which the issuer of a check may print a check on blank check stock, and also print thereon visibly obscured information providing traceability. Another system has been reported for on-site check printing in which a microscopic character representation of the check amount is printed on the check.
There remains a need for a simple and reliable system which can perform both authentication and verification of documents by encrypting and decrypting information read from the face of the document, as opposed to imaging the face of the document and processing a representation thereof.